Historically, toxic baits for controlling crawling insects such as cockroaches have been water-based. With cockroaches especially, water is presumed necessary for good bait performance. Unfortunately, water-based bait products rapidly lose effectiveness due to water loss, rancidity, break-down of active ingredients and other factors. Studies of water-based paste baits have confirmed that water loss, repellant properties of active ingredients, and insecticide resistance are the most important factors affecting bait performance. Appel, A. G., J. Econ Entomol. 85 (4):1176-1183 (1992), Robinson, W. H., Proceedings of the National Conference on Urban Entomology 77-91 (1992), and Rust, N. K., "Managing Household Pests", in Advances in Urban Pest Management, G. W. Bennett and M. Owens (eds), Van Norstrand Reinhold, N.Y. 335-368 (1986).
One approach to improve on water-based insecticide products has been to use a dust or paste composition which contains a so-called water powder with the insecticide. This water powder is water entrapped within hydrogenated soybean oil, as described in U.S. Pat. No. 5,820,855. Another water-free fat-based pest bait product is described in U.S. Pat. No. 5,464,613. These compositions are paste forms and includes as a major ingredient a fat-based carrier. Unfortunately, dust compositions have disadvantages such as drifting of the material when applied. Although paste products do not drift, they can be difficult to apply and require an applicator for applying pastes in cracks and crevices. Additionally, paste bait products cannot be easily and effectively applied into void areas which can be major pest harborage areas. Also, paste baits can rapidly lose water in hot, dry areas and become ineffective. There is thus a need for improved pesticide compositions especially for use in wet or moist areas, as well as in hot, dry void areas.